The invention relates to tools for machining various materials, and more particularly to rotary tools for making holes in various materials. The invention may be most advantageously used for making holes in sheet materials.
At present, rotary tools are known for making holes comprising a working part and a shank for clamping in a portable tool, such as in a portable drill. The working part of the known rotary tools is made with the profile of a drill, tap, reamer or combination, e.g. drill/tap.
With the use of such tools, an axial feed force should be, however, applied which depends on the diameter of the working part, properties of the material being machined, rotary speed of the tool and other factors.
It should be noted that in a number of applications feed forces attain values inadmissible for portable tools for which the limit feed force is normally specified by Safety Rules.
It is widely known to use, in portable drills, various mechanical, pneumatic and hydraulic feed assemblies which provide a required feed of the working part of the tool during drilling. These feed assemblies, are, however, complicated, cumbersome and costly.
It making holes with portable tools, the operator cannot, in some cases provide for application of the required feed force, e.g. because of the absence of restraint or for other reasons. In many applications there is no restraint for abuttment of the feed assembly of a portable drill. In some instances, a hole is to be drilled with several tools in the order of increased diameter so as to reduce the feed force required, and such method is associated with unproductive time losses for change of tools.